Art of removing suspended particles from fluid or gaseous bodies



A. F. NESBIT.

ART OF REMOVING SUSPENDED PARTICLES FROM FLUID OR GASEOUS BODIES.APPLICATION FILED NOV. 17, 1914.

1,357,201. Patented Oct. 26,1920.

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% 464 if m A. F. NESBIT. ART OF REMOVING SUSPENDED PAR TICLES FROM FLUID0R GASEOUS BODIES. APPLICATION FILED NOV. 17,1914.

1,357,201, Patented O0t. 26, 1920.

i E 30 I E 66 Q, Q -fl Q if UNITED STATES PATENT. OFFIGE.

ARTHUR F. NES BIT 0F WILKINSBURG, PENNSYLVANIA, ASSIGNOR T0 INTER-NATIONAL PRECIPITATION COMPANY, A CORPORATION OF CALIFORNIA.

ART OF REMOVING- SUSPENDED PARTICLES FROM FLUID 0R GASEOUS BODIES.

earner.

Specification of Letters Patent.

Patented Oct. 26, 1920.

Application filed November 17, 1914. Serial No. 872,618.

To all whom it may concern: I

Be it known that I, ARTHURF. Nnserr, a citizen of the United States,residing at Wilkinsburg, in the county of Allegheny and State ofPennsylvania, have invented new and useful Improvements in the Art ofRemoving Sus ended Particles from Fluid or Gaseous odies, of which thefollowing is a specification.

This invention relates to the art of removing particles of matter fromfluid bodies in which they are held in suspension.

Heretofore electrical discharges have been employed for the purpose ofremoving suspended matter from fluids, which discharges may consist ofbrush discharges, the electrical wind, the corona discharge, etc. Thenature of these discharges is not well known but they involve, amongother'phenomena, secondary ionization of the fluid medium, which may bedue to the collision of the ions with the fluid particles, or it may bedue in part to electromagnetic waves or pulses. It is known, however,that electrical discharges of this kind result in a copious productionof ions. Any discharge can be effected only by the use of one or moreelectrodes placed in or near the said fluid medium, and the electricaldischarge may be caused to take place from one electrode, which isdesignated the active electrode. In the art of removing matter fromfluids the electric field may be made very concentrated near the activeelectrode in order that the luminous, heat, and ionization effects maybe localized in the. neighborhood of said electrode. The secondaryionization produced in this region results in the production of a largenumber of positiveand negative ions. 'The ionshaving charges dissimilarto that of theactive electrodeare attracted toward it andare said togive up their charge to this electrode as ionsof the said sign ofcharge. Ions possessing a sign of charge that is the same as that of theactive electrode are repelled from it and if the secondary ionization issufliciently intense and continuous, this flow of ions will bedesignated as a stream of ions, or an electric current.

One of the objects of the present invention is to utilize thesephenomena in removing suspended matter from fluids, by passing 'thefluids containing the matter to be removed between an active'and agrounded electrode, the latter preferably surrounding the former whollyor in part. It is obvious that the grounding of either electrode is amatter of convenience, and hereafter the term grounded electrode will beused to designate the electrode near which the intensity of theelectrical field is comparatively weak. A further object is to providevariable and shifting electric fields throu h which the fluids arecaused to pass, where y the highest possible precipitation of thesuspended particles is obtained.

The shape of the grounded electrode may varyaccording to the work to bedone, depending upon the conditions under whic the fluids containing thematter to be removed are to be treated. These different conditions maywell be illustrated in the problems of the precipitation of smokeproduced in round houses, railroad tunnels,and

forth and particularly pointed out in the claims.

In the accompanying drawings 1-- Figure 1 is a diagrammatic viewillustrat-- ing my invention. Fig. 2 is a plan or end view illustratingthe relation of the electrodes in their simplest form. Figs. 3 and 3 andFigs. 4 and 4' are side and plan views respectively, illustrating thetheory of the present invention. Figs. 5 and 5 Figs. 6 and 6 and Figs. 7and 7 are side and plan views, respectively, of various modifications.Figs. 8, 9 and 10 are sectional views illustrating additionalmodifications. Figs. 11 and 12 are end views illustrating the manner inwhich fields areshifted by deposits on the active electrodes. Fig. 13 isa side elevation of another modification.

As above pointed out, it is a well known fact that the discharge ofelectricity into a gaseous or flui medium containing suscompleteprecipitation of these particles. To accomplish this result thegaseousvor fluid bodies are made to pass throughl the electric field. Itis evident, however, that pended particles gives rise to a more or lessin the part of the field where the dischar e is weakest there will befound the least ten ency toward precipitation. To illustrate, a wire,circular in cross section, may be placed a trifle out of the axis of asurrounding cylindrical casing or pipe of conducting material, and itwill be readily observed of the electrode systems or the stream flowofstrain lines.

ing through the field. Thus, in Fig. 2 the center of the pipe is at 10and the axis of the wire 11 is at 12 the distribution of the electricstrain lines eing somewhat as indicated by the lines 13 radiating fromsaid wire. If smoke, cement dust, fine ashes, alumina dust, or similarsuspended particles should be blown through the pipe 10,"

the density of the suspended particles within the pipe will be greatestin that portion of the electric field which. has the least number Thatis, that part of the gases carryin the suspended particles which passesthroug the region at will experience a more complete cleaning orprecipitation of its contained particles than. in the region y.

If, in lieu of the eccentric wire, a group of two or more smooth andbare wires, either parallel to each other, or uniformly twisted togetheror twisted about a central wire is placed within a pipe or casing whichmay or may not be grounded, the electric field will have its strainlines somewhat as illustrated in Figs. 3 and 4", Whatever may be thepotential above the corona formation value, up to the sparking voltage;in other Words, the ionization field will be dissymmetrical in fieldintensity on a cross section of the electrode systems of the streampassing through the field, each of the wires producing the unsymmetricalintensity efi'ect with respect to the portion of the field which isproduced by it. In Figs. 3, 3*, 4 and 4, the wires 15 are parallel toeach other throughout their length and inclosed by the surroundingelectrode 16. The wires are so placed that they form a symmetricalgrouping about an imaginary line coinciding with the axis of the pipe,2'. e. the wires are eccentric with respect to the axis of the pipe. Thestrain lines are as represented, and 17 and 18, Fig. 3, and 19, 20, and21 in Fig' 4, are the least active portions, due to the mutuallyrepellent action of the strain lines in the cusp-like pore tion of themedium about the surfaces of the wires, and symmetrical about the lines17-18, Fig. 3 and 19, 20, and 21 of Fig.

4*, respectively. As the particleTaden gaseous or fluid stream passesthrough the pipe there is a tendency of the suspended particles to flockinto this neutral or inactive cuspal zone, as it might be called. Justas 1'0 soon as this occurs there is an increase in the dielectriccapacity of this cuspal zone in the case of all gaseous or fluid bodiesfor which a greater density of suspended particles corresponds to a lessresistance to the flow or discharge of electricity. As a result of thisincrease in the dielectric capacity of this region, the electric strainlines having their origins or terminals on these wires, flock morethickly into this same region and simultaneously become less dense inthe regions where the electrical field was formerly of greatestintensity. It will thus be seen that the electric strain lines aresubjected to a shifting of their ends and origins between the directions17-18, and 19, 20 and 21, or the converse. This swaying, traveling, orswinging electric fieldhas a beneficial effect in dislodging the depositor accumulation of the suspended particles which may havebeenprecipitated upon the inner walls of the pipe or conduit.

The tendency of these cusp-like regions to become filled with tarry orother substances of greater dielectric capacity than air will afteratime. cause the accumulations to assume the appearance indicated inFigs. 11 and 12, in which the deposited material is indicated at 22.Just as soon as the radial depth of this deposit becomes suf- ,1 ficientfor the voltage difference maintained between the wires and the pipe tocause a disruptive discharge along such path, there will be an immediatebreaking loose of a large patch of this accumulation about the cuspalzone through which the disruptive discharge takes place. The result is adislodgment' of this deposit, in the vicinity of the spark, not onlyalong the lines indicated,

but more or less along all the region's symmetrical to the radial linesindicated, and to some distance along the wire either side of the pointatwhich the discharge occurs. This dislodgment is also aided by thetendency of the wires to be set into more or less feeble vibration.These operations are occurring simultaneously and are .associated withthe lateral shifting of the strain lines in their to and fro excursions,and may take place at any region throughout the length of i the wires.What has thus far been said about the groups of wires in Figs. 3, 3, 4and 4, may be extended to twisted or I braided groups of wires asindicated in the other fi res.

In Figs. 5' to 9 the electricfield takes the form of a double cork screwof greater or less pitch depending upon the closeness with which thetwists are made. Thus, the cprona discharge from each wire takes placemost 1 the symmetrical axis of their grouping.

This corkscrew form of field causes the smoke, fumes, or otherparticle-laden gaseous or fluid bodies to take up a more or lesshelicalor tortuous 1path during its passage through the pipe. ence, fora given length of pipe such groupings of smooth wires as suggested byFigs. 5, 6 and 7 will have the advantage of being more or lessself-cleaning of deposited material due to the swinging action of thecorkscrew field and at the same time will be equivalent to a longer pipewith straight wires within it. The wires should be quite small indiameter consistent with the tension to which they are subjected toprevent anything but the slightest vibration, and at the same time havethe electric field as intense as possible at the surface of the ,wires.The more intense the field is maintained at the surface of the wires,corresponding to a value of the voltage difference between the wires andthe pipe, (just below the break down voltage) the more rapidly willionization take place, and the precipitation of the suspended particlesin the gaseous or fluid bodies will be more complete. In Fig. 7, 60indicates the central wire about which the other wires be wound.

he spirals may be wound'more or. less closely together as indicated inFigs. 5, 6, and 7, or they may be separated in diameter and pitch asindicated in Fig. 8. Such a spiral, helical, or corkscrew grouping ofwires for the active electrode will give a very decided tendency for thegaseous and fluid streams to assume a tortuous or helical form of pathin their travel through the' pipe or surrounding conductor. When such agrouping is made of fine wires the tendency for harmonic vibration ofeach individual helix may be destroyed by tying them together atintervals. Again, there may be one helical spiral within another, and ofsmaller diameter, and of the same or reversed winding, as illustrated inFig. 10. These cork-screw or spiral electric fields, by imparting to thegaseous or fluid bodies, a spiral or helical form of flow during theirpassage through the electric field, cause the said bodies as well as theparticles suspended therein, to be acted upon by a centrifugal forcewhich tends to throw them out radially toward the inner wall of thesurrounding conductor.

The centrifugal forces which/ are thus brought into existence play amore or less prominent part themselves in causing a separation of thegaseous and fluid bodies from the particles suspended therein. In otherwords the centrifugal process is quite efiicient, in itself, in roducinga separation of suspended particl es from gases, for

the reason that there is usually a considerable difference in the massesof the particles to be separated. This is particularly true in theapplication to the separation of ore dust from blast furnace gases, inthe cement and aluminum industries, and in fact wherever the relativedensities of the gaseous or fluid bodies and the suspended particles arevery different. A more intense localized spiral field may be obtained asshown in Fig. 13 by placing within the uter electrode 56 and against itsinner wall, a helical wall 55 of the same pitch as that of the activeelectrode 57 here described. This electrode 57 is indicated simply indotted lines; but may take any of the forms herein described. Thecentrifugal forces here introduced are very important.

he same results may be obtained by the use of a single conductor 30, asillustrated in Fig. 9, or a fine wire wound upon the V- ridge of aninsulating or non-conducting su port. In Fig. 9 the conductor is provied with a helicalgroove or thread 31. The pitch of this groove or threadmay vary, depending upon the number of spiral turns into which it isdesired to throw the gaseous or fluid stream during the passage throughthe electric field and also upon the velocity of these same particleladen streams. The distribution of the electrical strains in all of thefigures in which the spiral field is maintained is indicated at 25. Aswill be readily understood, a discharge electrode, such as described,will, where the radial distance between the edge and the outer electroderemains constant throughout the length of the edge, even though the edgebe inspiral form, produce a zone which will be continuous throughout thelength of the edge, a result which is obtainable by the use of a tubularouter electrode, circular in cross section, with the axis of thedischarge electrode on the symmetrical axis of the tube.

In the construction shown in Figs. 6, 7, and 9 it will be furtherapparent that the spiral discharge electrodes offer but slightresistance to the direct flow of the gases and that the radial length ofthe flow path is substantially equal to the radial length of theionization zone.

It will be obvious to those skilled in the art that the process ofproducing variable and shifting electric fields is modified slightly bythe form assumed by the closed conductor or pipe surrounding the wires,and I accordingly do not desire to limit myself to the pipe of circularcross section, which is merely used for illustrative purposes. Inpractice the central group of Wires and the surrounding pipe orconductor are commonly termed the active and grounded electrodes,respectively. The active electrode constitutes the group of wires sincethe electric field is most intense at its surface and it ishere that theionization is most intense. The-outer electrode or pipe is usuallygrounded as a precaution against danger and as a means of savinginsulating material. 7

The electric current maybe supplied in any suitable or desired manner.In the drawings, Fig. 1, l[ have illustrated a generator 40, and atransformer 41 having a primary loW potential circuit and a highpotential circuit, the latter being connected to a suitable rectifyingdevice 4A: of any preferred construction? In the method of cleaning theelectrodes by a disruptive discharge, as herein described, it isnecessary to have certain predetermined relations between the capacity,self induction, and resistance factors 'of the high tension circuit sothat the discharge is disruptive when the v distance between theelectrode and the deposited matter is less than the disruptive potentialdistance of the gaseous or fluid bodies. For the purpose of producingdisruptive or oscillatory discharges various sultable conditions may beimposed upon the electrical circuits connected to the active andgrounded system of electrodes. For the v purpose of illustration,besides the resistance, capacity and self-induction of the transformeritself, I have shownin Fig. '1"

certain combinations of resistances 4:5: and 46, capacities 47, 48,self-inductances 49, 50,

and spark gaps 51, 52, distributed in the secondary circuit, so thatunder working conditions electro-magnetic oscillations of the properfre%ency and damping factor are produced. hese resistances, capacities,self-inductances and spark gaps are placed in whatever parts of thecircuit found most suitable or desirablefor the results desired, and forobvious reasons I do not limit myself to the precise arrangementillustrated, either as to the relative positions ofthe rectifiers,resistances, inductances and capaci- ,.ties, or of the type of rectifieremployed.

Having now described the manner of producing the variable and shiftingelectric fields of more or less complex form, what I claim as new andfor which I wish Let- 'ters Patent is hereinafter set forth 1. In theart of producing electrical precipitation of particles from fluid orgaseous streams, opposing electrode systems adapted to produce anionization field, the discharge system comprising a plurality of wiresconstituting the discharging means arranged spirally in the direction oflength of the system, each wire having its axis out of the axis ofsymmetry of the opposing electrode system to produce a dissymmetricalfield intensity on cross sections of the systems, field portions of likeintensity varying as to position relative to a longitudinal plane ofsuch field, whereby the stream will tend to flow spirally through thefield.

, 2. In the art of producingelectrical precipitation of particles fromfluid or gaseous streams, opposing electrode systems adapted to producean ionization field, the discharge system comprising a spiral dischar eelectrode constructed and arranged to ofler but slight resistance to thedirect 'fiow of the gases and having continuous 5. That improvement inthe art of produe ing electrical precipitation from fluid or gaseousstreams which consists in establishing a continuous ionization zoneextending spirally inthe direction of the length of the flow path andmaking the radial length of the flow path substantially equal to theradial length of the ionization zone.

6. That improvement in the artof producing electrical precipitation fromfluid or gaseous streams which consists in establishing a plurality ofcontinuous ionization zones in the flow path of a stream, said zonesextending spirally in the direction of length of the stream flow pathand making the radial length'ofthe flow path substantially equal to theradial length of the ionization zones.

7. A discharge electrode for electrical precipitating apparatus,consisting of a-conductor having projecting and dischargin portionsextending longitudinally thereo), said conductor being twisted so thatthe projecting and discharging portions extend spirally thereof.

- In testimony whereof I have hereunto set my hand in presence. of twosubscribing witnesses. I g

. NESBIT.

Witnesses B I Y W. J. Mocha.

